There has been known an image forming apparatus such as a laser printer which uses an endless belt so as to perform sheet conveyance, intermediate transfer and the like.
In this image forming apparatus, a belt cleaning device using a roller or brush is provided to remove foreign matters such as toner or paper powders attached on the belt. In the belt cleaning device, a cleaning roller which removes the foreign matters such as toner or paper powders contacts a surface of the belt.
For example, JP-A-2008-58475 describes a configuration where a cleaning roller is arranged to oppose a metallic electrode roller which is provided inside an annular conveyance belt, with the conveyance belt being interposed therebetween, and the toner or paper powders are electrically removed.
In the above-described configuration, since the electrode roller is made of metal, an electric discharge is more apt to occur between the electrode roller and the conveyance belt at upstream and downstream sides in a moving direction of the conveyance belt than between the cleaning roller and the electrode roller. That is, since the electrode roller formed of the metal has an electric resistance smaller than that of a roller made of semiconductor material, charges accumulated on the conveyance belt are apt to flow towards the electrode roller.
If the electric discharge occurs between the conveyance belt and the electrode roller, a polarity of the foreign matters attached on the conveyance belt may be changed. If the polarity is changed, the foreign matters cannot be collected by the cleaning roller.